This invention relates to color connecting photographic film printers and, more particularly, to improved apparatus for detecting malfunctions of the light valves that execute color corrections in a film printer.
Film printers are employed to expose a reel of raw film to the frames of photographic images on a reel of master film while the master film and raw film are transported together. Light control operations are commonly executed during the exposure process in high quality film copying operations. In particular, red, green, and blue color corrections are made by so-called light valves at the beginning of each scene of the master film to compensate for the different lighting conditions under which the master film was produced and different film characteristics. Typically, light from a light source is split into the component colors blue, green, and red by dichroic mirrors. The three light components are transmitted through respective light valves to adjust the proportional intensity of each color component. The adjusted color components are recombined and the recombined color adjusted light is projected through an exposure aperture onto the film. Each light valve includes a bar type adder unit having a plurality of solenoid actuated slides. Binary signals representing the color correction are coupled to the slide actuating solenoids, thereby causing the adder unit to expand linearly by an amount depending upon which of the slide actuating solenoids have been actuated. This linear expansion is converted to an angular rotation by a vane memory. The angular position of the vane memory is then sampled by energizing a vane solenoid, which is turn moves vanes in the light valve into the path of the particular color component, i.e., red, green, or blue, an amount determined by the angular position of the vane memory. The slides are also movable as a unit when a trim adjusting knob is turned. (This permits an initial adjustment to be made depending upon the film characteristics.)
Balint et al U.S. Pat. No. 3,502,409, which issued Mar. 24, 1970, discloses a malfunction detecting system for film printers. Specifically, the contacts of a reed switch associated with each side are opened and closed responsive to a pivotable shield member that lies in the path of the associated slide. Thus, the position of each slide is represented by the state of the corresponding reed switch, i.e., open or closed. The reed switches are mounted on a stationary block and therefore do not move with the slides when the trim adjusting knob is turned. To detect a malfunction, the states of the reed switches are compared with the states of the stages of a slide register in the form of memory relays. When the comparison indicates that the reed switches do not match the contents of the slide register, an error indicator is actuated.